This invention relates to new and useful improvements in friction furnaces. Friction furnaces are those in which a source of power is used to rotate an inner drum within a stationary outer drum with a relatively small annular clearance between the two drums. The inner drum is usually provided with a roughened surface and oil is provided in the base of the drums which normally stand vertically, to generate the friction heat as the inner drum rotates. As the inner drum rotates, the oil in the base of the stationary drum, moves upwardly to partially fill the annular space and heat is extracted from the outer drum by various means including air passed over the outer drum, it being understood that heat transmission is by conduction and convection.
Such vertical drum friction furnaces take considerable time for the inner drum to get up to its full speed due to oil drag and even under optimum conditions, the oil appears to rise only approximately one-third of the space between the two drums so that the vertically situated friction drum is relatively inefficient.